Two field experiments were carried out at Shandweel Agricultural Research Station in 2009 and 2010 seasons to study the effect of sowing dates and first irrigation( Al-Mohayat) on growth, earliness, seed cotton yield and its components of Giza 90 (Gossypium barbadense L.). A split-plot design with four replications was used. The main plots were assigned to sowing dates (March 25, April 10 and April 25). Al-Mohayat  irrigation time i.e., two, three and four weeks after sowing were assigned in the sub-plots. The results indicated that early sowing (March 25) significantly increased days to first flower, days to first open boll, number of open bolls/plant, seed cotton yield per plant and per feddan in both seasons. While, plant height at harvest and location of first fruiting node branch were decreased. Meanwhile, number of fruiting branches/plant, boll weight and  number of plants at harvest/feddan were not  significantly affected by sowing dates in both seasons. Delaying Al-Mohayat irrigation to four weeks after sowing significantly increased plant height at harvest, location of first fruiting node branch and days to first open boll in both seasons. While,delaying Al-Mohayat irrigation to three weeks after sowing significantly increased number of open bolls/plant, seed cotton yield per plant and per feddan in both seasons. Meanwhile, number of fruiting branches/plant, days to first flower, boll weight and number of plants at harvest/feddan were not significantly affected by Al-Mohayat irrigation.The interaction between sowing dates and Al-Mohayat  irrigation had a significant effect on plant height at harvest, boll weight, number of open bolls/plant, seed cotton yield per plant and per feddan in both seasons. While, number of fruiting branches/plant, days to first open boll and number of plants at harvest/feddan were not affected in both seasons. Generally, best results were obtained when cotton plants were sown early (25 March) and Al-Mohayat irrigation (three weeks).